The present disclosure relates to a fixed and/or moveable system, in particular in or for vehicles, for example cars. The system operates with common or related time bases for indication of the time of detected or generated events in the system, and/or in a system or systems connected to this.
The present disclosure also relates to a device for effecting the establishment of functions carried out by two or more units (nodes) comprised in the system in a fixed and/or moveable system, in particular in or for vehicles, for example cars. The device can relate to arrangements for detection, control, analysis and/or simulation of comprised units.
The use of systems of this type in, for example, vehicles, is already known and reference can accordingly be made, among other things, to the patent applications and patents submitted by and granted to the same applicant as the present applicant. In the respective systems, the message and information (data) transmissions are carried out using or in accordance with protocols of a known type, which can be of a standardized type, for example Universal Serial Bus (USB), Controller Area Network (CAN), Local Interconnect Network (LIN), Ethernet, IEEE 802.11x, Infrared (IR), Wireless USB (WUSB), etc.
With this type of system, there are problems in determining events and/or time functions without relatively complicated and bandwidth-intensive arrangements. There is, for example, a desire to be able to determine the occurrence of the events and/or give indications of the time so that the normal traffic can be utilized to indicate the relevant time and/or occurrence of the event, for example, without extra hardware needing to be involved. The object of the disclosure is, among other things, to solve this problem. There is a need, in the respective module units, to be able to operate with preferably small resources with the object of simplifying the construction of the units. There should also be great freedom of choice in the construction of systems and their relationships. This disclosure also solves this problem.
A major problem in distributed embedded control system is to synchronize the generation of events in different nodes to each other in a timely manner, e.g., reading sensor values, execution of movements, releasing of power etc. The main solution to this problem is to create a global time and synchronize clocks at each node. Usually the time synchronization is made at the communication level. Typical examples are TTCAN, TTP and FlexRay protocols in the vehicle industry and SERCOS in the factory automation industry. All of these communication protocols are time triggered and it is a common opinion that safety critical distributed embedded control systems have to be based on a time triggered communication. An alternative to synchronizing clocks is to have each module relying on its own local clock and have a time translator recalculating the time of each clock to a common global time, but it has been regarded impossible to do in real time.
U.S. Pat. No. 5,896,524 suggests a method to recalculate clock readings by associating event pairs related to each other. However, such conventional methods cannot be used in realtime (e.g., see column 1, line 65 through column 2, line 4). What is needed is a method and apparatus that calculates the relationship between local clocks at run time. What is further needed is to calculate the relationship between local clocks and a global time base at run time.
U.S. Patent Application Publication US2006-0143345A1 shows that, in realtime systems at run time, it is more efficient to use different time domains within the system, wherein each time domain is created according to the need of cooperating nodes, rather than to rely on a global time. However, a global time may be better used for analyzing a system.
Each system in which the disclosure can be used can be regarded as individual, one or more series or sequences of events that are related to each other in time and space. There can be different time descriptions and time frames within one and the same system. Smaller systems can be comprised in the system, which in turn can, now or later, be comprised in other systems. During the first stage, the “drawing board” stage, of a system development, it is expedient to relate all the events to one and the same time frame, for example related to the physically defined second. The degree of coordination that is required of the different events in order for the required system function to be achieved can be analyzed in a first stage. In a second stage, an analysis of the relationship of the individual events to each other can indicate that other time frames and the utilization of knowledge concerning the association of different events to each other can simplify the design of the final system and the description, verification and validation of the same. The disclosure simplifies these development processes.
For analysis or verification of systems, there is a need not only to timestamp events that have occurred, but also to know with what precision and/or accuracy the timestamping is carried out.
It can happen in systems that different parts of the system relate events to different time bases, which in turn are related to each other.
Analysis and monitoring instruments of different types for vehicles are often based on standard computers with operating systems, for example a personal computer (PC) with WINDOWS XP®. The operating system (OS) simplifies the development of the software at the price of precision of timestamping of external events. Therefore special units are introduced between the PC and the bus system that, among other things, comprise a clock for timestamping of incoming time messages. For example, with the utilization of the program CANANALYZER from the company VECTOR, a CANCARDXL from the same company is connected to the PC. The CANCARDXL has a local clock and can timestamp messages from two CAN busses. If there is a need for several CAN busses, an additional CANCARDXL unit must be connected to the PC and the two CANCARDXL units must be connected to a coordination unit via a coaxial cable arrangement in order to synchronize their local clocks to a common time. By utilizing the disclosure, timestamping can be carried out with great precision, utilizing only components to be found as standard in the PC.